Unconfirmed news reports after the Connecticut school shooting that gunman Adam Lanza had been diagnosed with Asperger’s syndrome, a mild form of ­autism, have prompted strongly worded statements from autism advocacy groups that the developmental disorder was not associated with “planned violence.”

Psychologists who treat people with ­autism point out that premeditated violence toward others is not one of the traits associated with the disorder in the psychiatric diagnostic manual. While some individuals may thrash out violently when feeling emotionally overwhelmed — usually those at the extreme end of the autism spectrum — there is no evidence linking the condition to the type of forethought ­required to pack guns into a car, shoot through the entrance of a locked school, and methodically gun down tiny strangers in pigtails and baseball caps.

“Autism is related to different ways of processing information in the brain, but not in those areas related to violence,” said Dr. Donnah Nickerson-Reti, a neurodevelopmental psychiatrist with a private practice in Boston.

Advertisement

Generally, people on the autism spectrum tend to be driven by rules and logic, making them highly cognizant of laws that should not be broken and taking extreme efforts not to break them, she said.

Get Fast Forward in your inbox:

Forget yesterday's news. Get what you need today in this early-morning email.

“Can autistic individuals get flooded emotionally and act irrationally?” said Nickerson-Reti. “Of course they can, like everyone else, but that’s not a defining characteristic.”

There is a dearth of studies measuring how often any sort of psychotic or delusional ­behaviors occur in the context of an autism diagnosis. “What little research we do have suggests that these people are much more likely to be victims of violence than perpetrators,” said epidemiologist David ­Mandell, who conducts research at the University of Pennsylvania on improving the quality of autism care. That’s because individuals with the developmental delays typical of autism tend to have a hard time reading social cues or detecting danger signs from someone threatening them. Typically, ­autism associated with impulsive aggressive behaviors ­occurs in those who are low-functioning, not with milder forms such as Asperger’s syndrome, which Lanza was purported to have had.

“Most of the folks who come here are kind, gentle, and peace-loving,” said Dania Jekel, executive director of the Asperger’s Association of New England in Watertown. “It’s sort of a shame for them that this association with violence has been made.”

Michael Appell of Newton said his 24-year-old son who has Asperger’s has not decided whether to reveal his condition to his new boss at a high-tech firm. “My son has never had any violent tendencies, but many people may now paint a different profile of him, which makes this whole thing shocking and disconcerting.”

Advertisement

Some of those who treat ­autism note that they occasionally see patients who pose a risk of harming others, even when not acting out on ­impulse.

“I’ve had autistic patients like this,” said Dr. Martha ­Herbert, a pediatric neurologist at Massachusetts General Hospital and co-author of “The ­Autism Revolution.” “But I wouldn’t say it’s the autism causing those behaviors. We need to learn more about the underlying biology to see how much autism overlaps with other psychiatric conditions.”

Autism has been linked to a wide range of medical problems such as gastrointestinal illnesses, low bone density, and asthma, but researchers have not determined whether it is associated with psychiatric conditions such as bipolar disorder and schizophrenia, which, when untreated, have been ­associated with violence.

What is not known is how often those who assault loved ones during fits of rage are misdiagnosed with a form of ­autism when they really have a form of psychosis or a personality disorder. “There’s not a lot of cohesion among psychiatrists about how to define the entire diagnostic category of autism including Asperger’s,” said Nickerson-Reti. “We don’t ­always see the same thing” with a given set of symptoms.

Many mental health practitioners are upset by a new definition of autism that is expected to be published in the updated DSM-V psychiatric diagnostic manual in 2013. It eliminates subgroups of the disorder such as Asperger’s and distills the diagnosis to a simple gradient from mild to severe.

Advertisement

But most agree the most pressing issue is getting help to those who need it most. “How do we identify people who are at increased risk of mental illness and intervene in a meaningful way?” said Mandell. That said, the rate of mental illness does not vary much among industrialized countries, but the rate of gun violence does. “I think the overwhelming difference,” Mandel added, “is access to firearms.”